Cold Spring Mayor Doug Schmitz told MPR's The Daily Circuit that many people in the community didn't hear about the incident until Friday morning.

"There's a lot of people in shock wondering how we could lose such a nice young officer," Schmitz said. "Tom was a very well-liked kid."

Authorities describe the Cold Spring shootingMPR Photo/Tim Nelson

Schmitz said Decker led firearms training for the city's fire department, and would often joke around with the participants.

"He kept everybody loose, you know, took his job serious but was kidding around to keep the people feeling like they're just loose, you know, they're not stressed out," Schmitz said.

He was a Rocori High School graduate, and a 2002 graduate of Alexandria Technical College, receiving an A.A.S. Degree in Law Enforcement. Decker served as a police officer first in the City of Isle, in Mille Lacs County, in 2002. He moved to Watkins in Meeker County in 2003, and then to the Kimball Police Department in 2004. In 2006, Decker joined the police department in Cold Spring and Richmond.

Decker grew up on a dairy farm south of Cold Spring. He was one of eight children. His mother said Decker worked the night shift and would sometimes check in with her in the morning, as he wrapped up his workday. She said they talked almost daily.

Cold Spring shootingAP Photo/The St. Cloud Times, Eric Stromgren

Authorities have released few details about the incident, but they said Decker and another officer were making a welfare check on 34-year-old Ryan Larson in an apartment above Winners Sports Bar and Grill on Main Street when the shooting took place on a nearby street. Decker was shot twice and died at the scene.

Larson was arrested about an hour later and was being questioned. He has not been formally charged in the case.

Stearns County Sheriff John Sanner and officials from the state Bureau of Criminal Apprehension refused to speculate on what triggered the attack. The investigation is ongoing, they said.

Larson had lived in nearby Rockville recently, and the BCA and a crime lab were in town Friday afternoon. Authorities said they were conducting interviews around the state in connection with the case.

Larson has had some other run-ins with the law, including a misdemeanor disorderly conduct charge from 2009. A spokeswoman for St. Cloud Technical & Community College told The Associated Press that Larson was a second-year machine tool student.

Condolences from officials from across the state poured in.

"Officer Decker died while protecting his fellow citizens," Gov. Mark Dayton said in a written statement. "For his heroism, we will be forever grateful."

Newly appointed Minneapolis Police Chief Janee Harteau got choked up Friday after the City Council unanimously approved her appointment Friday morning.

Harteau said she didn't know the slain officer, but said she didn't have to know him in order to feel a sense of loss.

"It's a tough day because last night an officer was killed in the line of duty — basically murdered in cold blood. And it doesn't matter if you're part of this police department or any police department, it's a family member," she said.

The last time a Stearns County officer was killed was in January 1996, when Brian Klinefelter was shot to death while attempting the arrest of three suspects in a liquor store robbery.

Police in downtown Cold Spring, Minn. Friday morning, Nov. 30, 2012, following a Thursday night shooting that killed one officer. Cold Spring is southwest of St. Cloud.MPR Photo/Conrad WilsonView full galleryOfficer Tom Decker, 31, and another officer responded to a call about a potential suicide in an apartment above Winners Sports Bar and Grill on Main Street in Cold Spring, Minn. when Decker was ambushed and shot behind the bar late on Thursday, Nov. 29, 2012.MPR Photo/Tim NelsonCold Spring police chief Phil Jones speaks to reporters Friday, Nov. 30, 2012 about the shooting death of Officer Tom Decker.MPR Photo/Tim NelsonIn this photo provided by the Stearns County Sheriff is Ryan Larson, 34, of Cold Spring, Minn. Larson was arrested at the scene of a shooting Thursday, Nov. 29, 2012 in Cold Spring, Minn., where police officer Tom Decker died in what authorities are calling an ambush killing. The county prosecutor is reviewing the case for charges.AP Photo/Stearns County Sheriff